CCNP - ospf->nssa->no-redistribution

Author

ospf->nssa->no-redistribution

2000-12-21, 9:08 am

http://www.cisco.com/univercd/cc/td...tm#xtocid179473

"AREA NSSA
(...)
Syntax Description:
(...)
no-redistribution
(Optional) Used when the router is a NSSA ABR and you want the REDISTRIBUTE command to import routes only into the normal areas, but not into the NSSA area."

QUESTION:
->"REDISTRIBUTE command" on an "ABR"?
i thought it was an ASBR command...

thanks for your comments
frans

2000-12-21, 9:38 am

this note complete my initial question that is:
- how can "REDISTRIBUTE" command to be set on an ABR?
http://www.cisco.com/univercd/cc/td...tm#xtocid984511

"If possible, avoid using explicit redistribution on the NSSA ABR because confusion may result over which packets are being translated by which router."

thanks
frans

2000-12-21, 3:32 pm

quote:
Originally posted by emo francois:
QUESTION:
->"REDISTRIBUTE command" on an "ABR"?
i thought it was an ASBR command...

An OSPF router may be internal or ABR (and non-ASBR), and a "redistribute" command will cause the router to become ASBR.

The cause-effect relationship is:

issue "redistribute" command --> router becomes ASBR

not

router is ASBR --> you may issue "redistribute" command

Cheers!

2000-12-22, 6:49 am

thanks dmaftei,
but how do you interpret the AREA NSSA Syntax Description:

"no-redistribution
(Optional) Used when the router is a NSSA ABR and you want the REDISTRIBUTE command to import routes only into the normal areas, but not into the NSSA area."

thanks for your comments
frans

2000-12-22, 6:33 pm

I should warn you that NSSA was never a favorite of mine, so I never bothered to understand it thoroughly. However, here's what I think about "no-redistribute" with NSSA ABRs.

I assume you know how Not-So-Stubby-Areas and stub areas are different. I also assume you know about the type 7 LSA (like a type 5 LSA, but flooded in a NSSA).

Imagine you have a NSSA ABR, let's call it ROUTER, attached to the backbone and to area 1, which is a NSSA (of course...). ROUTER is also an ASBR; that is, it imports routes external to your AS. You want the external routes learned by ROUTER to be known in your AS, EXCEPT for area 1 (don't ask me why you want to do this

). You'll use the "no-redistribute" option when you declare area 1 as NSSA.

If, on the other hand, you don't declare area 1 with "no-redistribute", whenever ROUTER will learn an external route, if will advertise the route in the backbone (in a type 5 LSA) AND in area 1 (in a type 7 LSA).

Does this answer your question?!

Cheers!

[This message has been edited by dmaftei (edited 12-22-2000).]

Sponsored Links